 Okay, so I guess let's try this one here. So it starts out giving you the reaction equation, and it's balanced actually. So you don't even have to worry about balancing it, so that's cool. The first thing it asks you is determine if the reaction is a redox or a non-redox reaction. So in order to do that, you're going to have to figure out what the redox numbers and all this stuff. Remember, uncombined elements, like things by themselves, like H2 or Na or whatever, that don't have a charge, they're zero. So oxidation number of both these hydrogens is zero, oxidation number of both of these fluorines is zero. So these are combined, this is a combined element, this is a compound. So the oxidation numbers are going to be different than zero. Fluorine's oxidation number is only negative one, that's it. So if this is going to be negative one and the whole compound is overall zero, then H has to be plus one, like that. So let's just erase that and we'll put the oxidation numbers from the beginning, so H over here was zero, F over here was zero, H over here was plus one, F over here was minus one, that's what we figured out what H was. So did they change or did they not? Yes, they changed, so this is a redox reaction. If you want to think about it, fluorine got reduced and hydrogen got oxidized, if it asked you that question, what got reduced, what got oxidized? The thing that got reduced was fluorine, because it combined with hydrogen. Remember, that's one of the rules, okay? So here, let's just write that down, reduced, fluorine, oxidized, H. Okay, so the next question, it says, what's the type of chemical reaction? Well, you've got two things, right, A plus B, combining into AB, right? That's a combination. So that's a combination reaction. I don't know what these were, A or something like that, this would be B. That's a combination. RXN is short for reaction. Can I erase that part? Oh yeah. Okay, cool. And then the last part, the hard part, is how many grams of HF gas are produced when reacted with five moles of F? Well, it probably should say F2, a bunch of that's a typo. So how many grams of HF? So we're looking for the mass of HF, we don't know. But we do know the number of moles of F2, which says it's, we'll just say 5.00. Well the one cool thing is that it gives you this in moles, so you don't have to convert it to moles, okay? If it gave it to you in grams or liters or something like that, you're going to have to convert it to moles, okay? Why is that? It's because the reaction equation gives you a conversion factor for the different things in the reaction on the basis of moles, okay? So the reaction that you're looking, or the conversion factor you're looking for is F2 to HF, how many moles to how many moles, right? So if you want to write that conversion factor down, it's one mole of F2 equals two moles of HF, right? Because for every one mole of F2 you have, you can produce two moles of HF, does that make sense? Yes. Okay, so that's like your conversion factor, okay? So that's what you're going to put here. Because you're trying to figure out, well, you're not trying to figure out that anymore, what you're trying to figure out now is the number of moles of HF. And from that you can get the mass of HF, okay? But you can figure out the number of moles of HF from the number of moles of F2, okay? So how do we figure that out? Well, we just use our conversion factor, right? Moles of F2 times what? My conversion factor. Well I want moles of HF, right? So I'm going to put two moles HF to one mole F2. Where did I get that from? Remember, I got that from the coefficients of the reaction equation, one to two, got it? Hopefully you can see moles of F2 will cancel out. So we get the number of moles of HF is going to be five times two. I didn't bring my calculator today but I'm assuming that I can do that in my head, hopefully. You can do that in your calculator in a few, if I got it wrong, tell me. Okay, so ten moles of HF, I'll just keep it at three sig figs for right now and the whole thing is going to have to be at three sig figs. So that gives us the moles of HF, right? That doesn't give us the mass of HF. How do we get the mass of HF? Well, we need to figure out a conversion factor, right? Another conversion factor. So we're going to have to figure out, well what is the conversion factor that goes from moles of HF to grams of HF? You know what that is? What is that conversion factor called? The mole or mass? We call that, right? I know you know, it was on the tip of your tongue, right? So how would you figure that out? We've got to get the mass of H and then the mass of F, right? So let's just do it this way. So we'll say 1.008 is H plus 19.00. So the molar mass of HF is going to be 20.01, and that's grams per mole. Remember, that's the kind of text message way of writing it, right? So you can write it all on one line, but we don't write it that way in chemistry. That's our conversion factor, right? So we've got 1 mole of HF, right? This is grams per mole of HF, if you really want to say, right? Equals how many grams? Well, it must be 20.01, correct, like that, right? That makes sense. And then what do we do? So what are we looking for, the mass of HF? Yeah. Well, we're going to take the number of moles of HF that we have, 10.0, moles HF. And do we have a conversion factor that goes from moles to grams? What is it called again? The molar mass. The molar mass, yeah, very good. And to figure out the molar mass, you just add all the atoms up, right? And moles has to be on the bottom, right? Grams at the top. So 1 mole HF is going to be on the bottom, 20.01 grams HF, if you want, whatever, on the top. Cancel. Cancel. And then I just do that number times 10, and of course, to three sig figs. This does not count in your sig figs, okay? So the sig figs were only from here. This is where I got my sig figs from. Okay, that was the only thing given to us in the problem. So if we do that, well, it's going to be 200 grams of HF. But if we leave it like that, it's implying that there's only one sig fig, right? Yes. So let's just put a dot there. We can write it like that, and that can be our answer, or we could write it like 2 times 10 to the 1, 2 grams HF in scientific notation. Either one is fine, okay? So are there any questions before we turn that off?